My earlier U.S. Pat. Nos. 4,205,740, 4,044,876, 4,304,521 and 4,759,676 disclose pulsating gravity-type conveyors which are particularly desirable for conveying palletized loads, and which are also highly desirable for use in storage-rack systems for permitting "first in-first out" storage of palletized loads. In this known conveyor or storage-rack system, the loaded pallets are supported directly on conveyor rollers, which rollers are disposed in longitudinally adjacent relationship and are supported by a carriage or rail structure which enables the rollers to vertically reciprocate in a cyclic or repetitive manner. This arrangement physically causes the palletized loads to be intermittently lifted and lowered relative to a longitudinally extending stationary brake which extends at a slight decline relative to the horizontal. The pallets are stopped by the brake when the pallets and rollers are in their lowered positions, whereas the slope of the roller arrangement enables limited gravity-induced forward advancing of the pallets when the rollers are in their raised positions.
While the known arrangement described above has proven highly successful and desirable for transporting and storing palletized loads, particularly in storage rack arrangements, nevertheless in some storage racks the spacial or size requirements prevent optimum utilization of such systems in terms of permitting maximum utilization in the number of vertically stacked bays, or use of the system due to the extensive length of the individual bays. For example, with known gravity-type systems of the type described above, the slope of the conveyor as it extends longitudinally along the bay typically involves a vertical drop of about six inches for each ten feet of horizontal conveyor length. Since such conveyors when incorporated into storage racks typically extend from a minimum length of about 40 feet to a maximum length of as much as 200 feet, the vertical drop over such lengths can vary from as little as about two feet to about ten feet. Because of this vertical drop, when several bays each incorporating a conveyor are stacked vertically on top of one other, the number of stacked bays is limited not only by the height limitation of the building, but also by the vertical drop caused by the slope of the conveyor. Thus, optimum utilization of available space, particularly vertical height, cannot always be achieved.
The present invention thus represents an improved gravity-type conveyor which enables gravity-type forward advancing of loads over relatively long distances in an incremental or steplike manner while enabling the conveyor in the elongate direction thereof to be substantially horizontal or level, and thereby eliminate the elongate sloped structural relationships normally required with conventional gravity-type conveyors.
The present invention also represents an improved gravity-type conveyor which is believed to improve upon known conveyors of the general type described above by permitting more efficient utilization of vertical height available within a building, and hence permitting utilization of a larger number of vertically stacked bays in a storage rack within the same amount of available vertical space then was previously possible.
More specifically, with the improved arrangement of the present invention, the gravity-type conveying system may be associated with each bay of a storage rack, which bays are stacked vertically one above the other, with several stacks or columns being disposed horizontally adjacent. The individual inventive conveyor as associated with each bay, however, extends horizontally between input and output ends so that a palletized load as positioned on the conveyor at the input end is at the same elevation as the palletized load stored at the output end. The conveyor, however, incorporates a pulsating load-engaging arrangement which enables the loads to be vertically raised and lowered in a pulsating or cyclic manner, and at the same time enables the individual palletized loads to be gravity-urged forwardly along the conveyor through sequential small distances or steps to effect forward advancing of the loads from the input to the output end of the conveyor.
With this improved arrangement, as described above, the overall available height can be more efficiently utilized since the individual bays do not require additional height at one end to compensate for slope inasmuch as the individual conveyors extend horizontally. This enables a greater number of bays to be vertically stacked within a predetermined height, and thus enables higher density storage of palletized loads within a particular building volume.
Further, the improved arrangement results in the input ends of the bays being generally lower than previously possible, and thus facilitates the positioning of loads onto the input ends of the bays. This arrangement also enables the palletized loads to remain horizontal at all times, even during the gravity-urged advancing of the palletized loads along the conveyor. This thus avoids having to tip or tilt the loads, thereby providing greatly improved load stability. This is particularly desirable in situations where the loads are pallets having other objects such as bottles or the like loaded thereon, since the continual horizontal stability of the loads provides greater safety of handling and less tendency for the objects to slip or move off of the pallet.
While the improved level gravity conveyor of this invention is highly desirable for incorporation into storage racks of the general type described above, this improved level gravity conveyor is also highly desirable for use as a conveyor for general load-advancing purposes while permitting such advancing to be performed by gravity while carried out in a safe and controlled manner.